Many benign pathologies or oral anomalies that appear in
children's soft tissues can be treated by dentists. Conventional
treatment of these pathologies involves the use of the cold knife,
electrocautery or cryosurgery (using a gas expansion system or a cotton
bud soaked in liquid nitrogen) [Ishida and Ramos-Silva, 1998]. Laser
treatment can be added as an alternative or complement to conventional
methods [Gontijo et al., 2005]. There is extensive literature on soft
tissue management using lasers [Miserendino and Pick, 1995; Bradley,
1997; Strauss, 2000; Stabholz et al., 2003; Kotlow, 2004; Strauss and
Fallon, 2004; Brugnera et al., 2006; Kato and Wijeyeweera, 2007; Kotlow,
2011]. Some oral lesions that are susceptible to laser treatment are:

All of the above are indications for the use of high power lasers.
In addition, low power lasers have bio-stimulating (tissue
regeneration), analgesic and anti-inflammatory effects, which are of
great use in oral and dental trauma (lacerations, abrasions and
concussions), wound healing, paraesthesia, myalgia and temporomandibular
disorder [Pinheiro et al., 1998; Brugnera et al., 2006], root canal
disinfection and reducing post-operative pain of endodontic surgery
[Kreisler et al., 2003]. Lasers also have been used to reduce pain once
fixed appliances have been fitted [Lim et al., 1995; Turhani et al.,
2006].

Types of lasers used in soft tissue treatment

The word LASER is an acronym of light amplification by stimulated
emission of radiation. This is a type of electromagnetic energy that is
directional, collimated, monochromatic and coherent (in time and space).
These properties distinguish lasers from disordered, incoherent
radiation [Nelson et al., 1988]. There are several types of laser. Each
one emits light at a specific wavelength that is determined by the gain
medium (solid, liquid or gas) [Pick and Powell, 1993]. The effects of a
laser on an irradiated tissue depend on the amount of light energy
absorbed, which in turn depends on the laser wavelength and the tissue
optical properties. Consequently, each laser has a therapeutic
application of choice. Not all lasers produce the same effects. In
addition, the effect of one type of laser varies according to the tissue
and the emission parameters and can even have different effects on the
same tissue. In some cases, a specific treatment can be carried out with
more than one type of laser. The output (the amount of energy released
per unit of time) can be varied by adjusting the laser unit. Handpieces
deliver the energy to the target tissues and contain an optical fibre
(tip). Thus, the laser energy can be focused or defocused on a larger or
smaller area of application, depending on the distance between the tip
and the tissue. A higher output is obtained when the laser is applied to
a smaller area [Coluzzi, 2000].

High power, therapeutic or surgical lasers (high level laser
therapy) have a clear thermal effect. They focus a large amount of
energy on a small space and produce ablation, incision, carbonisation,
vapourisation and coagulation of the tissue. Out of the high power
lasers described below, the first four are used for soft tissues and the
last two for hard and soft tissues.

The Argon laser is the only high power laser that emits visible
light: all of the others emit infrared light. Its use in oral surgery is
limited to cutting action on soft tissues. Above all, it is indicated
for the surgical treatment of vascular or pigmented lesions. Some argon
lasers can be used in polymerisation instead of halogen lamps
[Hildebrand et al., 2007]. Wilkerson et al. [1996] performed pulpotomies
in primary teeth using this laser. Verco [2007] undertook
electrosurgical lingual and maxillary fraenectomies using an Argon laser
beam. The combined device they used is called the ExplorAr Argon Plasma
Cutting Electrodes (APCE) with Argon Beam Coagulator (ABC)[R]. The APCE
makes a fast cut and the ABC coagulates blood.

The Diode laser is a solid-state semiconductor laser associated
with aluminium, gallium and arsenic. The output is 3.5-15W. Diode lasers
have an 800-980nm wavelength in the range of visible and invisible near
infrared light. Beams can be emitted in continuous or pulsed
(interrupted) mode [Coluzzi, 2000]. Continuous mode is used for soft
tissue procedures. This laser has high absorption in tissues pigmented
with haemoglobin, melanin and collagen chromophores and low absorption
in dental hard tissues. Consequently, it is indicated for surgery of
oral soft tissues close to dental structures that does not involve
excessive bleeding [Gontijo et al., 2005]. Diode lasers are small and
inexpensive. The optical fibre delivery system touches the soft tissue
and can be used for ablation, incision and excision (cutting,
vapourisation, curretage, coagulation and haemostasis). This type of
laser produces a rapid increase in the temperature of the target tissue
[Romanos and Nentwig, 1999; Coluzzi, 2000]. Consequently, it is
important to control the time of application and the working power to
prevent overheating of adjacent tissues, which can lead to necrosis.

Diode lasers should never be used in contact with hard tissue. In
periapical and periodontal surgery it is used for disinfection purposes.
In endodontics, a fine optical fibre can be used to improve disinfection
of root canals along with biomechanical preparation. Romanos and Nentwig
[1999] used this laser to perform fraenectomies. In a preliminary study
in an animal model, Silvestri et al. [2007] indicated that the diode
laser can arrest the formation of the third molar if the mucosal area of
the gum is irradiated when the molar is in its bud stage.

Two other neodymium lasers are of interest. The Nd:YAG (wavelength
= 1060nm and output = 0.3-6W) and Nd:YAP (wavelength = 1340nm and output
= 5W). The behaviour of neodymium lasers is similar to that of diode
lasers. They can operate at high or low output [Bradley, 1997] and have
limited use in oral surgery. They can be used as an alternative to
C[O.sub.2] lasers, as they produce precision cutting, haemostasis and
simultaneous disinfection [Braggett et al., 1999]. However, their
cutting efficiency is slightly slower than C[O.sub.2] lasers. They are
useful in the treatment of vascular lesions and gingival melanin
pigmentation [Matsumoto and Hossain, 2002; Vesnaver and Dovsak, 2006].
In addition, they act as a disinfectant in endodontics and periodontics,
as they are an effective bactericide [Brugnera et al., 2003]. An Nd:YAG
laser in combination with a diode laser is available on the market.
Fornaini et al. [2007] used this laser to perform treatments on
orthodontic patients, including fraenectomies, fenestrations of
unerupted teeth and gingivectomies, with excellent results.

Carbon dioxide lasers (gas medium; recommended output = 3-10W;
wavelength: 10,600nm) have a very high water absorption coefficient,
regardless of the colour of the tissue. This laser is well absorbed by
all soft tissues that have high water content. The effect on adjacent,
non-targeted tissues is minimal. No direct contact with the target
tissue is required. The beam can be focused (cutting effect) or
defocused (vapourisation). These lasers generate a lot of heat and burn
tissue fast. The charred layer should not be removed, as it acts as a
biological cover [Tamarit et al., 2005]. In oral surgery, C[O.sub.2]
lasers produce excellent intra-operative coagulation of small blood
vessels and immediate sterilisation of the surgical field and reduce the
inflammatory reaction and scar formation. Consequently, they are widely
used in the surgical management of oral soft tissues. An incisional
biopsy should be carried out prior to treatment with this laser [Huang
et al., 2007]. Carbon dioxide lasers are very safe and effective for
soft tissue surgery in developing countries [Kato and Wijeyeweera,
2007]. With this laser, the risk of disseminating cancer cells or
producing bacteraemia is virtually nil [Tamarit et al., 2005].

The Er,Cr:YSGG: (erbium, chromium, yttrium, scandium, gallium and
garnet laser) type of laser has a 2,780nm wavelength. It cuts calcified
tissues (enamel, dentine, cement and bone) safely and effectively, due
to a hydrokinetic system of photon liberation in an air-water spray, and
can be used instead of a rotary instrument. Ablation of enamel and
dentine occurs when the organic components absorb the irradiated energy,
which produces vapourisation of the water and of the hydroxyl ions in
the apatite mineral. At low output, it desensitises dentine [Jacobson et
al., 2003; Raucci-Neto et al., 2007]. Due to its versatility, this type
of laser is one of the most commonly used in paediatric dentistry. It
can be used on soft and hard tissue and is associated with a reduction
in discomfort, oedema, scarring and wound shrinkage. The air-water spray
allows histological studies to be carried out on removed lesions, as the
tissue is not overheated during the procedure [Boj et al., 2005a,
2005b].

The Er:YAG (Solid state medium of garnet, aluminiumscandium and
yttrium stimulated with erbium) is an invisible infrared laser of
2,940nm and is a pulsed laser that uses an optical fibre delivery
system. It is effective on hard and soft tissues, similarly to the
slightly older Er,Cr:YSGG laser. It is useful for soft tissue surgery
that is not extensive [Gontijo et al., 2005]. The fibre-optic delivery
system can be used to disinfect root canals along with the conventional
biomechanical preparation, with results similar to those of 1%
hypochlorite solution [Brugnera et al., 2003].

Argon, diode, neodymium, Er:YAG, Er,Cr:YSGG and C[O.sub.2] lasers
have been approved by the USA Food and Drug Administration (FDA) for
oral surgery [Keller et al., 1998]. The use of these lasers in various
surgical processes has been well documented [Pick and Colvard, 1993;
Coluzzi 2000; Martens, 2003; Stabholz et al, 2003; Strauss and Fallon,
2004].

Laser safety

There are several contraindications for laser therapy, of which
operators should be aware [Basford, 1995]. In addition, the following
safety measures should be taken into account. The eyeball should not be
directly or indirectly (through reflection) irradiated when visible or
infrared radiation is used at wavelengths of 400-1400nm, due to the risk
of retinal damage. Consequently, the dentist, patient and anyone in the
vicinity of the treatment area must use safety goggles as indicated by
the manufacturer. This measure applies to the use of any type of laser,
including soft lasers.

The skin of staff and patients should be protected to ensure that
no tissues outside the surgical field are burned. The interaction of the
laser with a tissue has a photo-thermal effect. Depending on the
absorption, the temperature can produce transient hyperthermia
(42-45[degrees]C), coagulation (70-90[degrees]C) or carbonisation
(>200[degrees]C). Lasers with the highest absorption in soft tissues
(C[O.sub.2] laser) rapidly produce temperatures of 1,700[degrees]C at
the point of application. However, less heating occurs in adjacent
tissues than with other lasers that have lower absorption coefficients
(diode and Nd:YAG lasers). Overheating of adjacent tissues may lead to
necrosis. The accumulated thermal effect depends on the time of
application (continuous emission or pulsed). Erbium lasers produce less
thermal damage, as they are pulsed and use air-water as a cooling
system. In addition, they are highly absorbed by intrinsic water
[Strauss and Fallon, 2004].

Advantages of the laser over conventional surgery

Analgesia. The use of lasers reduces the amount of local analgesia
required and can reduce the perception of pain in some cases [Boj et
al., 2005a]. Authors such as Jacobson et al. [2003, 2004] and Boj et al.
[2006a, 2006b] using an Er,Cr:YSGG laser and Fornaini et al. [2007] with
Nd:YAG and diode lasers performed dental treatments on children without
local infiltration analgesia. Other authors did use analgesia [Kopp and
St Hilaire, 2004], although doses were lower than normal in some cases
[Kato and Wijeyeweera, 2007; Boj et al., 2009].

Haemostatic properties. These properties are significant, due to
the high vascularity of the oral cavity [Martens, 2003]. They are
extremely useful in vascular lesions and in areas with a rich blood
supply, such as the sublingual region, in the case of frenectomies
[Matsumoto and Hossain, 2002]. The carbon dioxide laser provides the
best intra-operative control of bleeding, which enables precise surgery
to be performed, as it is easier to identify anatomical structures when
there is no bleeding in the surgical field [Kopp and St Hilaire, 2004;
Kato and Wijeyeweera, 2007]. The Er,Cr:YSGG laser also has anticoagulant
properties when the percentage of air-water is reduced, which produces a
greater thermal effect [Wang et al., 2005]. The argon laser has also
been used as a coagulator in areas with a high density of blood vessels,
such as the lingual fraenum [Verco, 2007]. Erbium lasers have less of a
haemostatic effect than C[O.sub.2] and Nd:YAG lasers [Strauss, 2000;
Strauss, 2004].

Sutures. The need for sutures is eliminated, as haemostasis enables
wounds to heal by secondary intention. Exceptionally, some authors have
used sutures after C[O.sub.2] laser use [Kopp and St Hilaire, 2004].

Lasers are cicatrizants. They improve wound healing, which occurs
faster and with less scarring than after conventional treatments. Lasers
are good treatment options for ulcers and mucositis [Wong and
Wilder-Smith, 2002]. Healing is fastest after the application of erbium
lasers, as they have a low thermal effect [Wang et al., 2005]. In
addition, the defocused use of a C[O.sub.2] laser at the base of a
lesion completes haemostasis and enables immediate contraction of the
surgical site, with a 30-40% reduction in wound size. As no mucosal
tissue is lost, unaesthetic scar formation caused by wound tension is
avoided [Kopp and St Hilaire, 2004; Kato and Wijeyeweera, 2007].

Antibacterial/disinfectant properties. These properties enhance
post-operative recovery and reduce the required dose of antibiotics
[Turkun et al., 2006]. According to Kato et al. [2007], lasers are very
useful in developing countries where patients have high post-operative
morbidity and mortality, as infections are prevented.

Anti-inflammatory properties. Treatments that are undertaken with
C[O.sub.2] and Er,Cr:YSGG lasers cause less oedema and post-operative
pain, which reduces the required doses of analgesics and
anti-inflammatory drugs. As the C[O.sub.2] laser cuts soft tissue, it
seals nerve endings, blood and lymph vessels, which reduces the
inflammatory reaction [Tamarit et al., 2005]. The anti-inflammatory
properties of low level lasers can be used to treat muscle contractures
and traumas [Turkun et al., 2006].

Vibration. The patient does not feel any vibration, pressure, or
the contact of the optical fibre on the tooth, as occurs with a rotary
instrument. This increases a patient's collaboration [Keller et
al., 1998; Jacobson et al., 2003] and acceptance of the procedure
[Genovese and Olivi, 2008].

Post-operative care. Lasers improve post-operative comfort, due to
haemostasis, the lack of sutures, and the pain reduction. This is very
useful in young patients [Fornaini et al., 2007]. In papers on
fraenectomies performed with lasers and with conventional techniques, it
was observed that there was less post-operative pain and discomfort,
less functional complications and more patient satisfaction after the
laser therapy [Haytac and Ozcelik, 2006; Kara, 2008].

Discussion

As stated in the introduction, laser technology can be used in
children for the healing of most oral soft tissue lesions [Brugnera et
al., 2006; Martens, 2011; Olivi and Genovese, 2011] instead of
conventional methods (cold knife, electrocautery or cryosurgery) [Ishida
and Ramos-Silva, 1998].

The lasers of choice for soft tissue management are the Nd:YAG,
C[O.sub.2] and diode lasers [Parkins, 2000]. There is extensive
literature on soft tissue management with C[O.sub.2] lasers in children,
as this procedure is considered safe and has many intra-operative and
post-operative advantages [Tamarit et al, 2005; Kato and Wijeyeweera,
2007]. Some authors have used the Nd:YAG laser in children [Braggett et
al, 1999], whilst others consider that the combination of Nd:YAG and
diodes is more effective [Fornaini et al., 2007].

In recent years, the number of papers on the use of Er,Cr:YSGG
lasers in paediatric dentistry has increased as this type of laser is
very versatile, commonly used for hard tissue applications but can
readily be used for soft tissues [Hadley et al., 2000; Boj et al.,
2005b, 2006a, 2008, 2009]. The handpiece is similar to that of a
conventional turbine, which facilitates clinical management. The
technique is easy, reducing the duration of intervention. Its
haemostatic effect enhances visibility of the surgical area, which is a
major advantage in children's small mouths. Scarring is minimal (no
tissue retraction) and eliminates the need to suture. Lasers reduce
post-operative oedema, bleeding, infection and pain, and thus the use of
medications [Boj et al., 2007].

For labial fraenectomies, Gontijo et al. [2005] used a combination
of a diode laser to manipulate soft tissues and the Er:YAG laser for the
periosteum and the final collagen fibres. Erbium lasers allow for fast
healing, due to their minimal thermal effect, however surgery is not
completely bloodless, as it is with the C[O.sub.2] laser. Therefore,
compression is sometimes required to achieve haemostasis. Diode or
Nd:YAG lasers are preferable for the management of highly vascular
lesions, as they have a major coagulating effect [Tamarit et al., 2005].

The main laser safety measures are as follows. Eye and skin
protection is required for the dentist, patient and any staff in the
vicinity of the work area, to avoid retinal damage or burns. As a small
proportion of the laser energy is not used in the ablation process and
causes heat in dental structures, it is important to ensure that the
pulp is not damaged with certain lasers (C[O.sub.2] and Nd:YAG), that
should only be used for soft tissue ablation [Jacobson et al., 2003;
Matsumoto and Hossain, 2002], as a temperature rise of over 5[degrees]C
causes irreversible pulp damage. Consequently, erbium lasers, with the
correct proportion of air-water, are now used in hard tissue treatments
without tissue overheating [Rizoiu et al., 1998; Raucci-Neto et al.,
2007].

Certain types of laser (C[O.sub.2] and Nd:YAG) cause vapourisation
of the tissue, and if histopathological analysis is required, a biopsy
must be performed with a cold knife before laser surgery [Tamarit et
al., 2005]. Tran et al. [1999] and Boj et al. [2007a, 2009] indicated
that tissues removed with an Er,Cr:YSGG laser can be analysed
histopathologically, if they do not receive the impact of the laser on
removal, a low power (1.5W) is used and an air-water spray (10% water
and 11% air) prevents overheating of the surrounding tissue.

In the past, soft tissue surgical procedures were often rejected in
children, as problems with cooperation meant that they could not be
performed without general anaesthesia [Kotlow, 2004]. Several authors
have stated that the use of lasers causes less discomfort and is
well-accepted by young patients and their parents. Thus, lasers can
reduce psychological trauma and fear during the dental visit [Matsumoto
and Hossain, 2002; Gontijo et al., 2005].

The use of lasers in paediatric dentistry is still not widespread
despite their great versatility (some lasers are more versatile than
others). This could be due to the high cost of laser units, the lack of
education about lasers in undergraduate courses and the fact that
training is required. Nevertheless, in some dental treatments, the laser
is an irreplaceable tool, rather than the marketing device that some
dentists consider it to be. An increasing amount of literature on
clinical indications and protocols indicates that the laser is a tool
with great future potential in this field [Boj, 2005b].

Conclusion

Although the most commonly used laser for soft tissue management
has been the C[O.sub.2] laser, the Er,Cr:YSGG laser represents a
therapeutic alternative in most paediatric oral surgery, and produces
excellent results. Professionals must know the physical characteristics
of the laser and its interactions with biological tissues to be able to
use the device safely. It is also essential to know the indications of
each type of laser.